Synchrotron white-beam X-ray topography was used to characterize 2H-type crystals which had been grown via the chemical reduction of methyltrichlorosilane at 1400C. The crystals had the form of tapered needles which were about 0.5mm-long and had an 0.2mm-diameter hexagonal cross-section. Transmission Laue patterns confirmed the wurtzite structure of the crystals. Images which were recorded, in transmission geometry, from 2 different crystals revealed excellent crystal quality; as reflected by the presence of Pendellösung fringes. A close examination of these topographs, and of others recorded using different diffraction vectors, revealed no evidence for the presence of axial screw dislocations such as those previously reported on the basis of observations of spiral growth steps. No evidence was found for the presence of the so-called Eshelby twist which was associated with the presence of such dislocations. The absence of axial screw dislocations indicated that growth was not screw dislocation-assisted. It was suggested that the stacking sequence was determined by the thermodynamic growth conditions.

Synchrotron White Beam Topography Studies of 2H SiC Crystals. M.Dudley, W.Huang, W.M.Vetter, P.Neudeck, J.A.Powell: Materials Science Forum, 2000, 338-342, 465-8